A product search and a product purchase through a communications network, such as the Internet, have been popular. Under such circumstances, there has been proposed various search devices and product selling devices. Among the devices, there has been proposed a search device like, for example, Patent Literature 1. The search device presents highly-related phrases as suggestion words according to a search string input for product search. Here, for example, when a user inputs “TOKEI (Watch in Japanese)” as the search string for product search, the suggestion words mean candidates for the search including phrases highly related to the “TOKEI (Watch)”. The search device presents the suggestion words. As one example, when the user inputs “TOKEI (Watch)” as the search string, the search device presents “TOKEI (Watch) digital”, “TOKEI (Watch) men's”, “TOKEI (Watch) digital men's”, or a similar phase as the suggestion words. A space character between the “TOKEI (Watch)” and “digital” is used for performing an “AND search” of a plurality of phrases. In this example, the “AND search” is to acquire search results related to both the “TOKEI (Watch)” and “digital” phrases.